U.S. Pat. No. 5,244,216 discloses a fluid machine including:                a housing,        a rotational shaft located within the housing,        a stationary member connected to the housing,        a rotary member connected to the rotational shaft, and        a labyrinth seal configured to minimize or control fluid flow across the labyrinth seal, the labyrinth seal including:                    a succession of stationary steps formed on the stationary member, each stationary step including a radial wall portion extending substantially parallely to a longitudinal axis of the rotational shaft and an axial wall portion extending substantially perpendicularly to the longitudinal axis of the rotational shaft,            a succession of rotary steps formed on the rotary member, each rotary step including a radial wall portion extending substantially parallely to the longitudinal axis of the rotational shaft and an axial wall portion extending substantially perpendicularly to the longitudinal axis of the rotational shaft,            a plurality of stationary recesses, each stationary recess being formed in the radial wall portion of a respective stationary step, each stationary step defining a stationary projection delimited by the stationary recess formed on said stationary step and by the axial wall portion of said stationary step, and            a plurality of rotary recesses, each rotary recess being formed in the radial wall portion of a respective rotary step and adjacent to the axial wall portion of an adjacent rotary step located upstream said respective rotary step, each rotary step defining a rotary projection delimited by the rotary recess formed on said rotary step and by the axial wall portion of said rotary step.                        
Such a configuration of the labyrinth seal induces “obstacles” and restrictions to the leakage flow, and thus reduces fluid leakage through the labyrinth seal.
However such a labyrinth seal has flow passages and cavities of complicated shapes, which reduces the number of stationary and rotary steps available on a given axial sealing length, and which are complicated to manufacture. Further, such a labyrinth seal requires very accurate mounting and axial orientation between the rotating and stationary members. Furthermore, the configuration of such a labyrinth seal would be too fragile to be transferred to small and compact fluid machines.